1. Field of the Invention
The present invention relates to a vortex flowmeter, which is capable of detecting the flow rate of a fluid by detecting a vortex that is generated by the flowing fluid in a vortex generating body.
2. Description of the Related Art
Heretofore, a vortex flowmeter has been known in which a vortex generating body is disposed in a flow passage of a body through which a fluid flows, and a detector, which is constituted from a piezoelectric element or the like, is disposed on a downstream side from the vortex generating body. With such a vortex flowmeter, a Karman vortex is generated as a result of the fluid that flows in the flow passage flowing past the vortex generating body, and a pressure change of the fluid due to generation of the Karman vortex is detected and converted into an electric signal by the detector to thereby measure the flow rate.
As one such vortex flowmeter, for example, as disclosed in Japanese Laid-Open Patent Publication No. 11-014412, a flow passage is formed in the interior of a measurement duct that makes up the body of the vortex flowmeter, and a detector containing therein a piezoelectric element is housed in a bore that is formed in the measurement duct. A distal end of the detector is arranged so as to project into the flow passage, and between the bore and the detector, an o-ring is disposed to prevent ingress of fluid from the flow passage.
However, in the case that a chemical solution or purified water is utilized as the fluid in the aforementioned vortex flowmeter, contaminants, which are eluted from the o-ring that is made of an elastic material, enter into the fluid and contaminate the fluid. Further, if the fluid is a strongly alkaline or a strongly acidic chemical solution, the durability of the o-ring is reduced and sealing effectiveness is deteriorated.
Thus, for solving the problems discussed above, with the vortex flowmeter disclosed in Japanese Laid-Open Patent Publication No. 2002-195860, instead of using an o-ring, the detector is connected integrally with respect to a conduit through which the fluid flows, by ultrasonic welding, whereby an effective seal is maintained between the detector and the conduit, and contamination of the fluid or degradation of the sealing ability can be prevented.